334 TALKS ON MANURES. 



The actual cost of the ingredients, therefore, in the crop of 

 twenty bushels of wheat, would be about ten to twelve dollars. 

 But as this manure would furnish the ingredients for the 

 growth of both straw and grain, and it is customary to return 

 the straw to the land, after the first crop, fully one-third of the 

 cost of the manure might, in consequence, be deducted, which 

 would make the ingredients of the twenty bushels amount to 

 six dollars. Twenty bushels of wheat in England would sell 

 for twenty-eight dollars ; therefore, there would be twenty-two 

 dollars left for the cost of cultivation and profit. 



A French writer on scientific agriculture has employed 

 figures very similar to the above, to show how French farmers 

 may grow wheat at less than one dollar per bushel. At this 

 price they might certainly defy the competition of the United 

 States. It is one thing, however, to grow crops in a lecture 

 room, and quite another to grow them in a field. In dealing 

 with artificial manures, furnishing phosphoric acid, potash, 

 and nitrogen, we have substances which act upon the soil in 

 very differents ways. Phosphate of lime is a very insoluble 

 substance, and requires an enormous amount of water to dis- 

 solve it. Salts of potash, on the other hand, are very soluble in 

 water, but form very insoluble compounds with the soil. Salts 

 of ammonia and nitrate of soda are perfectly soluble in water. 

 When applied to the land, the ammonia of the former sub' 

 stance forms an insoluble compound with the soil, but in a very 

 short time is converted into nitrate of lime ; and with this salt 

 and nitrate of soda, remains in solution in the soil water until 

 they are either taken up by the plant or are washed away into 

 the drains or rivers. 



Crops evaporate a very large amount of water, and with this 

 water they attract the soluble nitrate from all parts of the soil. 

 Very favorable seasons are therefore those in which the soil is 

 neither too dry nor too wet; as in one case the solution of 

 nitrate becomes dried up in the soil, in the other it is either 

 washed away, or the soil remains so wet that the plant cannot 

 evaporate the water sufficiently to draw up the nitrates which 

 it contains. 



The amount of potash and phosphoric acid dissolved in the 

 water is far too small to supply the requirements of the plant, 

 and it ia probable that what is required for this purpose is dis- 

 solved by some direct action of the roots of the plant on com- 

 ing in contact with the Insoluble phosphoric acid and potash i-a 

 the soil. 



